A cost-effectiveness and cost-utility analysis of radiosurgery vs. resection for single-brain metastases

Brain metastases commonly arise in cancer patients and carry a poor prognosis. Both surgical resection and highly focused radiation techniques such as stereotactic radiosurgery (SRS) aim to improve clinical outcomes by controlling brain metastases at the local site. Determining which patient will benefit the most from surgical resection and/or SRS depends on that patient's clinical and tumor features. This chapter will discuss the landmark studies demonstrating the efficacy of surgical resection and SRS in the management of brain metastases as well as data attempting to compare the two modalities. Important considerations for deciding when to implement surgery and/or SRS will also be covered.

The cumulative incidence of brain metastasis at 5 years is approximately 5% in patients with breast cancer but is much higher in postmortem autopsy series. Overall breast cancer is the second most common cause of brain metastasis. Leptomeningeal metastatic disease is rarer at less than 1%. Metastatic epidural spinal cord compression preceding death due to breast cancer has been reported at 5.52%. Prompt diagnosis and treatment before the development of paralysis or paresis is associated with a better prognosis. Patients who present with cord compression without paresis can be adequately treated with radiation therapy (RT) alone (with or without corticosteroids). Patients who present with paresis or paralysis are less likely to regain neurologic function and have a worse prognosis. These patients require urgent evaluation and may be best treated with immediate decompression through surgery followed by postoperative RT.

The present study used cone beam computed tomography (CBCT) to measure the inter- and intrafraction uncertainties for intracranial stereotactic radiosurgery (SRS) using the Leksell Gamma Knife (GK).

Using a novel CBCT system adapted to the GK radiosurgery treatment unit, CBCT images were acquired immediately before and after treatment for each treatment session within the context of a research ethics board–approved prospective clinical trial. Patients were immobilized in the Leksell coordinate frame (LCF) for both volumetric CBCT imaging and GK-SRS delivery. The relative displacement of the patient's skull to the stereotactic reference (interfraction motion) was measured for each CBCT scan. Differences between the pre- and post-treatment CBCT scans were used to determine the intrafraction motion.

We analyzed 20 pre- and 17 post-treatment CBCT scans in 20 LCF patients treated with SRS. The mean translational pretreatment setup error ± standard deviation in the left-right, anteroposterior, and craniocaudal directions was −0.19 ± 0.32, 0.06 ± 0.27, and −0.23 ± 0.2 mm, with a maximum of −0.74, −0.53, and −0.68 mm, respectively. After an average time between the pre- and post-treatment CBCT scans of 82 minutes (range 27-170), the mean intrafraction error ± standard deviation for the LCF was −0.03 ± 0.05, −0.03 ± 0.18, and −0.03 ± 0.12 mm in the left-right, anteroposterior, and craniocaudual direction, respectively.

Using CBCT on a prototype image guided GK Perfexion unit, we were able to measure the inter- and intrafraction positional changes for GK-SRS using the invasive frame. In the era of image guided radiation therapy, the use of CBCT image guidance for both frame- and non–frame-based immobilization systems could serve as a useful quality assurance tool. Our preliminary measurements can guide the application of achievable thresholds for inter- and intrafraction discrepancy when moving to a frameless approach.

Brain metastases are common and the prognosis for patients with multiple brain metastases treated with whole brain radiotherapy is limited. As systemic disease control continues to improve, the expectations of radiotherapy for brain metastases are growing. Stereotactic radiosurgery (SRS) as a high precision localised irradiation given in a single fraction prolongs survival in patients with a single brain metastasis and functional independence in those with up to three brain metastases. SRS technology has become commonplace and is available in many radiation oncology and neurosurgery departments. With increasing use there is a need for appropriate patient selection, refinement of dose-fractionation and safe integration of SRS with other treatment modalities. We review the evidence for current practice and new developments in the field, with a specific focus on patient-relevant outcomes.